December 18, 2011

Modern human vs. Neandertal brains

The long-term trend in human evolution has been towards larger brains. Neandertals, however, had somewhat larger brains than us. It turns out that modern humans surpassed Neandertals in the development of some areas of the brain.

Nature Communications 2, Article number: 588 doi:10.1038/ncomms1593

Evolution of the base of the brain in highly encephalized human species

Markus Bastir et al.

The increase of brain size relative to body size—encephalization—is intimately linked with human evolution. However, two genetically different evolutionary lineages, Neanderthals and modern humans, have produced similarly large-brained human species. Thus, understanding human brain evolution should include research into specific cerebral reorganization, possibly reflected by brain shape changes. Here we exploit developmental integration between the brain and its underlying skeletal base to test hypotheses about brain evolution in Homo. Three-dimensional geometric morphometric analyses of endobasicranial shape reveal previously undocumented details of evolutionary changes in Homo sapiens. Larger olfactory bulbs, relatively wider orbitofrontal cortex, relatively increased and forward projecting temporal lobe poles appear unique to modern humans. Such brain reorganization, beside physical consequences for overall skull shape, might have contributed to the evolution of H. sapiens' learning and social capacities, in which higher olfactory functions and its cognitive, neurological behavioral implications could have been hitherto underestimated factors.

7 comments:

Why researchers age early: Neandertal brains are not larger than humans today. Neandertals buried, giving us good cranial preservation, but most Neandertal burials are males. Thus the sample is skewed male. That is why its average is high. BUT if you do a mid-sex average, or compare male and female means separately, N eandertal brain size is very close to western European averages. I first pointed this out more than 40 years ago, and nothing has changed on this issue since. To quote my mother, "OY"!

a) Neanderthals prior to the Wurm Glaciation (70,000 years ago) were smaller than the average for present day humans in cranial capacity (and particularly in their region),b) Neanderthals were larger in cc than the average of present day humans (and I think similar to present day high cranial capacity groups) during the Wurm Glaciation, c) Neanderthals were consistently somewhat smaller than contemporaneous Homo Sapiens d) Near Eastern Homo Sapiens and Neaderthals tend to have had higher cranial capcities than European species.

It's interesting that the abstract does not mention any specific areas where the Neanderthals are larger than us (if we have the same kind of brain size and we have some larger areas, the corollary is that we have some parts of the brain which are smaller). I'd guess that means that they are just kind of generally larger in all regions not specified as larger in present day Homo Sapiens.

Given the large body of evidence today that diet has a huge impact on cranial shape, I am actually disappointed John never mentions any of that. Clearly, abrupt changes sometime between ~10,000 and 5,000 ya are likely largely due to diet. Additional changes during Roman times as well, depending on the population sampled.

Basically, any place were muscles attach and/or stresses are large (top sides of the skull, lower-back cheek bones, lower jaw, chin, etc.) is highly shaped by diet during the growth and life of the individual.

I agree with Milford. If, in particular, the Krapina endocasts are included (per Holloway et al 2004), the average for Neandertals decreases considerably, and Upper Paleolithic AMHS, such as Brno, Chancelade, the Dolnis, etc, exceed modern averages, and are very close to Neandertals.

What puzzles me, however, is discussion regarding olfactory bulbs, which don't appear on endocasts, or leave any impressions by the cribriform plate.

Upper Paleolithic and Mesolithic Europeans are both larger than Neandertals. More recent Europeans have been smaller.

I wouldn't lump Krapina/Saccopastore with the later Neandertals for this comparison because of the large time involved. (I wouldn't lump these for dental dimensions, either). But if you do, as Ralph says, the Neandertal mean would be comparable to or smaller than today's depending how you compare.

I'd say that it's a gross overstatement that "today diet has a huge impact on cranial shape".

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